Distributed computer systems are known in the art. One such distributed computer system is a “content delivery network” or “CDN” that is operated and managed by a service provider. The service provider typically provides the service on behalf of third parties. A “distributed system” of this type typically refers to a collection of autonomous computers linked by a network or networks, together with the software, systems, protocols and techniques designed to facilitate various services, such as content delivery or the support of outsourced site infrastructure. Typically, “content delivery” means the storage, caching, or transmission of content, streaming media and applications on behalf of content providers, including ancillary technologies used therewith including, without limitation, DNS request handling, provisioning, data monitoring and reporting, content targeting, personalization, and business intelligence. Typically, the term “outsourced site infrastructure” means the distributed systems and associated technologies that enable an entity to operate and/or manage a third party's Web site infrastructure, in whole or in part, on the third party's behalf.
In a known system, such as shown in FIG. 1, a distributed computer system 100 is configured as a CDN and is assumed to have a set of machines 102 distributed around the Internet. Typically, most of the machines are servers located near the edge of the Internet, i.e., at or adjacent end user access networks. A network operations command center (NOCC) 104 manages operations of the various machines in the system. Third party sites, such as web site 106, offload delivery of content (e.g., HTML, embedded page objects, streaming media, software downloads, and the like) to the distributed computer system 100 and, in particular, to content servers (also referred to as “edge servers” if located at the aforementioned Internet “edge”) running on the machines 102. Typically, content providers offload their content delivery by aliasing (e.g., by a DNS CNAME) given content provider domains or sub-domains to domains that are managed by the service provider's authoritative domain name service, more details of which are set forth in U.S. Pat. Nos. 7,293,093 and 7,693,959, the disclosures of which are incorporated by reference herein. End users operating client machines 122 that desire the content are directed to the distributed computer system 100, and more particularly to one of its machines 102, to obtain that content more reliably and efficiently.
The distributed computer system may also include other infrastructure, such as a distributed data collection system 108 that collects usage and other data from the edge servers, aggregates that data across a region or set of regions, and passes that data to other back-end systems 110, 112, 114 and 116 to facilitate monitoring, logging, alerts, billing, management and other operational and administrative functions. Distributed network agents 118 monitor the network as well as the server loads and provide network, traffic and load data to a DNS query handling mechanism 115, which is authoritative for content domains being managed by the CDN. A distributed data transport mechanism 120 may be used to distribute control information (e.g., metadata to manage content, to facilitate load balancing, and the like) to the edge servers. More about the distribution of control information in a CDN can be found in U.S. Pat. No. 7,240,100, the disclosure of which is hereby incorporated by reference in its entirety.
As illustrated in FIG. 2, a given machine 200 comprises commodity hardware (e.g., an Intel Pentium or other processor) 202 running an operating system kernel (such as Linux or variant) 204 that supports one or more applications 206a-n. To facilitate content delivery services, for example, given machines typically run a set of applications, such as an HTTP proxy 207 (sometimes referred to as a “global host” or “ghost” process), a name server 208, a local monitoring process 210, a distributed data collection process 212, and the like. For streaming media, the machine typically includes one or more media servers, such as a Windows Media Server (WMS) or Flash server, as required by the supported media formats.
Client machines 122 include conventional personal computers, laptops, other digital data processing devices. Client machines also include mobile clients, which may include any a variety of mobile devices, often referred to as smart-phones or personal digital assistants (PDAs).
A CDN edge server is configured to provide one or more extended content delivery features, preferably on a domain-specific, customer-specific basis, preferably using configuration files that are distributed to the edge servers using a configuration system. A given configuration file preferably is XML-based and includes a set of content handling rules and directives that facilitate one or more advanced content handling features. The configuration file may be delivered to the CDN edge server via the data transport mechanism. U.S. Pat. No. 7,111,057, the disclosure of which is incorporated herein by reference, illustrates a useful infrastructure for delivering and managing edge server content control information, such as that for controlling file purge requests.
The CDN may include a storage subsystem (NetStorage), such as described in U.S. Pat. No. 7,472,178, the disclosure of which is incorporated herein by reference.
The CDN may operate a server cache hierarchy (Cache-H) to provide intermediate caching of customer content; one such cache hierarchy subsystem is described in U.S. Pat. No. 7,376,716, the disclosure of which is incorporated herein by reference.
For live streaming delivery, the CDN may include a delivery subsystem, such as described in U.S. Pat. No. 7,296,082, the disclosure of which is incorporated herein by reference.
The CDN may provide secure content delivery among a client browser, edge server and customer origin server in the manner described in U.S. Publication No. 2004/0093419 and/or U.S. Pat. No. 7,363,361, the disclosures of which are both incorporated herein by reference. Secure content delivery as described therein enforces SSL-based links between the client and the edge server process, on the one hand, and between the edge server process and an origin server process, on the other hand. This enables an SSL-protected web page and/or components thereof to be delivered via the edge server.